Role Models

Jack and Jill are having a frustrating time of it lately. They reach
for levers just beyond their grasp, crawl into spaces too small to fit,
and try to respond to instruments just out of their line of sight.

Sometimes it's painful. They smack their hands against cold metal by
trying to remove components they cannot maneuver. Strain against loads
too heavy to lift. Risk and even lose their limbs to unsafe
manufacturing processes.

Jill, Engineering Animation's female model, looks for design glitches that would
create obstacles for mechanics who fit the country's demographics for women.

It's a life even a crash dummy wouldn't envy. But it's just another
day at the office for Jack and Jill, the Everyman and Everywoman
characters in digital human factors software created by Engineering
Animation Inc. of Ames, Iowa.

Jack and Jill were created to simulate the reach, vision, strength,
and movement of actual human beings. They, and other human factors
software, are part of a new generation of digital creations designed to
analyze how people might interact with the three-dimensional environment
created by computer-aided design tools.

Aided by cheaper, more powerful computers, 3-D CAD models have grown
increasingly common and complex, encompassing everything from simple
components to cars and jet fighters. Over the past 15 years, developers
have designed software to reuse solid CAD models in a variety of ways.
Today, software programs and plug-ins use CAD data to visualize,
animate, simulate, validate, manufacture, and assemble parts digitally.

In essence, they create a virtual 3-D world. By inserting digital
humans into that virtual world-or stepping into it themselves-engineers
have found new ways to test designs for ergonomics, manufacturability,
maintainability, safety, and style.

Concurrent Engineering

The goal, of course, is to design better, higher-quality products
faster and cheaper by getting everyone from manufacturing and quality
through safety and maintenance involved in the process before settling
on a design.

A GM staff research scientist tests a virtual Pontiac Sunfire, which was created
in an immersive virtual reality system called CAVE, using GM's own software and
seen through 3-D glasses.

The approach, called concurrent engineering, has been talked about
since the quality revolution in the 1980s. Yet it has proven notoriously
difficult to master for companies making complex products, such as cars,
airplanes, heavy machinery, and electromechanical devices.

"What often happens is that product development is much more of a
serial process," said Bill Boswell, senior director of product
development at Engineering Animation. "People don't work in parallel."

According to Boswell, "Manufacturing engineers don't look at designs
until other organizations have signed off on them. There are horror
stories of people hanging almost upside down to change a hydraulic plug
because no one ever talked to the service people to see if they could
perform the task. If a service person had run an ergonomics model while
the part was designed, maybe she could have kept that from happening.
Without the underlying tools, it's hard to have a parallel process."

Bob Brown, president of Deneb Robotics Inc. in Troy, Mich., has the
same kind of concerns. "We're really the enabling tech for concurrent
engineering," said Brown, whose company markets Deneb/ERGO, human motion
and task analysis software that competes with Jack and Jill. Deneb is
owned by Dassault Systemes, developer of CATIA CAD software. The
company's goal, Brown said, is to reduce rework by 80 to 90 percent
before product launch.

"We're selling cost avoidance," he said. "No one likes to admit they
make design mistakes, but we ask them to look at the dollar value of
product and tooling change orders on their last program. If we can save
even 30 to 50 percent of that by proving out their products in a digital
environment, it would dramatically improve their bottom line."

Human models are especially useful in highlighting potential problems
in product assembly, use, and maintenance. These might include parts
positioned where hands cannot pivot to remove them, tractor levers that
short farmers cannot grasp, and production processes with safety
features that workers can circumvent.

Such problems often remain hidden in blueprints or CAD drawings. They
show up when engineers start crawling over physical mockups. In the
past, companies would correct problems discovered on a mockup, then
build a new mockup to correct issues arising from the previous set of
corrections. It cost time and money.

"Car companies built anywhere from 20 to 40, or even more, custom
mockups at a cost of $500,000 to $1 million each," said John MacKrell of
consultant CIMdata Inc. in Ann Arbor, Mich. "The cost in time is even
greater when you're trying to speed up product cycles to take advantage
of market trends." Today, he said, engineers want to catch most design
and assembly errors digitally and build mockups only at the end of the
process.

Error avoidance is the objective of the Virtual Product Development
Initiative at Lockheed Martin Tactical Aircraft Systems in Fort Worth,
Texas. The program is now in its third year. It uses Engineering
Animation's human factors software in conjunction with CAD,
visualization and animation systems, and manufacturing software.

"Our goal is to reduce cycle time and achieve as much as a 50 percent
reduction in manufacturing costs through error avoidance," said program
director Mary Ann Horter. "By doing everything digitally, we hope to
lower the cost of building mockups and reduce unplanned changes in the
development cycle."

A Tsunami of Changes

That means paying close attention to assembly. That's especially
important in the aircraft industry, where new fighters may have up to a
million parts. A simple change, such as widening a bulkhead hole to
improve access, could change the part's load-bearing properties and set
off a tsunami of other changes throughout the aircraft. That might mean
changing dies or machine specifications.

"We've caught lots of mistakes before we released parts," said
Tactical Aircraft Systems' manager of visualization, Robert Lynch Jr.
However, he's reluctant to divulge details about such secretive programs
as the F-22 Phantom and Joint Strike Fighter, a next-generation fighter
jet that Lockheed Martin is competing with Boeing to build.

Yet he does recall visualizing the assembly of JSF weapon bay doors.
"We were able to look at the assembly sequences when it was years away
from delivery," Lynch said. "The engineers actually watched an animation
of the way workers arranged the parts, then changed their minds about
the most efficient way to build the doors."

Assembly is also an issue at Deere & Co., the Moline, Ill., producer
of farm and heavy equipment. The company used Jack and Jill to locate an
access hole in a panel to confirm that any production line worker could
attach the panel to an assembly.

Deere engineers started by defining a fifth percentile Jill and a
95th percentile Jack. A fifth percentile woman is a digital manikin
whose anatomical traits rank among the smallest, narrowest, shortest,
and weakest 5 percent of all women. A 95th percentile man has size and
strength equal to or greater than 95 percent of men. By testing the
size, shape, and location of the access hole against different digital
populations, Deere ensured that all workers on its line could assemble
the part. Deere also uses human factors software from Division Group, a
San Diego unit of Parametric Technology Corp.

Digital humans also provide important insights into the design of
production and assembly equipment. "Presses and robots often have pinch
points where a person could be crushed," said Deneb's Brown. "So they
install palm buttons, safety devices located away from moving parts that
prevent the machine from working if the operator's hands are not on
them.

"A woman loading and unloading the machine might be able to rest her
elbows on those buttons and leave her hands at risk," he said. By
simulating the task with large digital populations, safety engineers can
determine before a machine goes into production whether anyone is likely
to circumvent its safety features.

Complex Assembly Interactions

As more companies outsource component manufacturing, their assembly
interactions grow more complicated. Autos, for example, increasingly
consist of large preassembled modules delivered from various sources and
put together on an automaker's assembly line.

First-tier suppliers not only have to simulate their own assembly
process, but how the component fits into the automaker's line. "The
auto-maker might share CAD data on car and dashboard shape, and the
component manufacturer would come back and show them the best way to
assemble the dashboard into a car," Deneb's Brown said. "Our systems
show how it fits and how someone using an ergonomic assist device can
snake the part through a door or frame and into its slot."

Division's dV/Safework is used to check accessibility of large equipment, such as a
Deere & Co. 310E backhoe.

If assembly is important, so is disassembly for maintenance. Nowhere
is this more important than in military and commercial aircraft. Some
stories of maintenance snafus have reached near-legendary status, such
as the simple plug that took two minutes to unscrew, only after hours
spent disassembling an entire surrounding subcomponent.

Such maintenance problems could prove deal-breakers for commercial
airlines, which earn their profits by flying expensive aircraft nearly
continuously. Anything that grounds them for prolonged periods costs too
much money. On the military side, the issue is flight-readiness.
Convoluted maintenance procedures reduce the amount of time that
high-performance fighters can stay in the air.

Boeing Co. uses its own proprietary human factors model, Boeing
McDonnell Douglas Human Modeling System, or BMD-HMS, to test a variety
of maintenance tasks in military and commercial aircraft. "We built it
over the past 10 years, pretty much from scratch," said Steve Rice, a
principal engineer and scientist at Boeing Phantom Works in Long Beach,
Calif. "We worked with optometrists, biomechanics, and other specialists
to define geometries, how the spine moves, motion algorithms-over 100
anthropomorphic measures."

In a typical application, Boeing had to determine whether a 50th
percentile female or fifth percentile male could replace an inert gas
bottle located under a transport's cargo floor. The human modeling
system showed that small mechanics could see and reach the fasteners.
The software's collision detection feature verified that no structural
parts interfered with the operation. The simulation saved Boeing the
time and cost of testing populations of workers on full-scale physical
mockups.

Using the same approach, Boeing highlighted assembly issues that
would be nearly impossible to identify without physical mockups. It
found, for example, that while a 95th percentile male could fit through
an access hole in a wing box, the bay's width and the distance between
the upper and lower stringers would restrict his full range of motion.

What works on the ground also works in orbit. "The International
Space Station has a requirement that every maintenance removal, such as
a smoke detector or valve, must be able to be carried out by a fifth
percentile Japanese female and a 95th percentile Western male," said
Phantom Works senior engineer and scientist Terri Graham.

By inserting manikins into a digital rendition of the space station,
Boeing proved that astronauts could inspect and reach the parts. The
human modeling system also created a swept volume around each tool that
defined tool clearance in the hands of the astronaut. As long as the
motions needed to remove the part stayed within the swept volume, the
job could be done without any problem.

"In the past, Houston would build water tanks where they would
suspend actual astronauts and have them perform tests on physical
mockups. Using BMD-HMS saved them millions," Graham said.

NASA asked Boeing to analyze several tasks aboard the space station's
laboratory node. Because it is so expensive to launch astronauts into
orbit, NASA strives to schedule their time fully. That means building
lots of mockups to estimate the time and number of people needed to
complete even the most mundane assignments.

Digital software makes the scheduling process easier and cheaper.
"The astronauts have to translate racks that look like telephone booths
with handrails on them from one part of the space station to the lab
module," Graham explained. "We ran a collision detection analysis to
determine whether it took one or two crew members to balance and move
the racks. We found that it took only one, and showed them where the
racks were a close fit and where collisions were most likely to occur."

Space may hold the glamour, but most human factor applications remain
firmly grounded here on Earth. Some of the most interesting analyses
involve brute application of digital speed and power. That's how
Battelle Research Institute of Columbus, Ohio, used Jack to locate the
grip height for a weed trimmer. It simulated a population of 5,000
people of different sizes to evaluate designs for comfort, reach, and
safety.

The U.S. Army used a more focused approach to evaluate amphibious
assault vehicle hull designs because it already knew the problem. Army
landing craft behave differently when cruising slowly and when skimming
over the water surface at high speeds. The analysis helped the Army
modify the hull so drivers could see the horizon no matter how fast they
traveled.

Immersive Virtual Reality

Sometimes, though, even the most powerful human factors models are
not enough. They may do a fine job of analyzing physical issues, but
some decisions, such as styling, ergonomics, comfort, and-for lack of a
better word-the "rightness" of a product, rest on subjective assessments
of engineering information. In this realm, 3-D models displayed on large
monitors simply do not convey the feeling of a design. Immersive virtual
reality does.

Immersive VR does just what the name implies: It catapults the viewer
into the picture. Naval captains feel as if they are sitting in the
control room of a nuclear submarine. Airline executives walk down the
aisles of aircraft still on the drawing boards. Automobile stylists sit
inside the interior of their latest creation and look out the window
(though they forgo the smell of new leather).

"Our experience has been that designers really obtain an enhanced
understanding of data when they are able to see it full size and in
three dimensions," said Robert Tilove, the group manager for
visualization and geometric modeling at the General Motors R&D Center in
Warren, Mich.

Tilove knows because he was one of the people who helped bring the
technology to GM during the early 1990s, when the entire virtual reality
field became a hot topic at university research laboratories.

GM already had half a solution. It used head-mounted displays to
flash images in front of each user's eyes. Unfortunately, the headsets
had poor color resolution-a red flag in style-conscious Detroit-and
their 3-lb. weight quickly became annoying. Equally important in an
enterprise as collaborative as auto design and construction, the
headsets isolated viewers. They did not all see the same image or one
another.

A Sun Microsystems researcher, Michael Deering, developed a small
pair of glasses containing electronic shutters. Instead of projecting an
image onto the glasses, Deering displayed it on a computer monitor.
Synchronizing the shutters with alternating right-eye and left-eye
images created the illusion of stereo depth. The technology is used by
StereoGraphics of San Francisco.

It made inspection of CAD models as intuitive as turning or bending
one's head. "It's a bit like a 3-D movie except it's interactive," says
Tilove. "If you sit far to the left in a 3-D movie, you'll see a
distorted image. Here, the system tracks your position and adjusts the
perspective. Many people can view the image and each other at the same
time to discuss and resolve engineering integration problems."

GM tested the system on a 39-inch monitor large enough to deliver
full-size views of hubcaps and instrument clusters. It then moved to a
power wall, which projects life-size 3-D images on a large screen from
the rear.

Going Into the Cave

Power walls did a good job of displaying a car's exterior, but
engineers couldn't get inside the car. That required displays on all
sides. The Electronic Visualization Laboratory at the University of
Illinois in Chicago had the solution. The lab called it a CAVE,
according to a 1993 paper, partly for the simile of the cave in Plato's
Republic, in which the philosopher discusses inferring reality, or ideal
forms, from their shadows projected on the wall. CAVE also stands,
somewhat redundantly, for CAVE Automated Virtual Environment.

The CAVE surrounds the viewer with four display walls: one in front,
two on the side, and one underneath. GM built the first company-owned
CAVE in 1994.

Engineers could now sit in a real seat while the computer drew the
image of the car around them. By pointing a laser wand, visible to
everyone in the room, they could highlight parts, push buttons, switch
levers-do everything but kick the tires.

GM's studios use the CAVE to visualize designs without building clay
models. "Obviously, it saves money," Tilove said. "More importantly,
though, it saves time. Instead of an iterative process of building
prototypes and evaluating them, we can build and modify computer images.

"We are able to look through the window and see if an A-pillar blocks
our view," Tilove continued. "We can check vision, obscurations, the
location of controls and gloveboxes. Then we can evaluate styling themes
and compare A to B to C. We can see how they look relative to a
competition's entry in the market."

The CAVE also lets engineers assess complex engineering data. In one
dramatic example, GM engineers simulate a crash at 30 mph using finite
element analysis. They then play back the incident in the CAVE.

"We can visualize every instant of time, what happens to the shape of
the vehicle, how it buckles, how the engine moves on impact," Tilove
explained. "Visualizing it in full scale helps engineers and designers
to interpret analysis results and suggest modifications to improve
performance."

How accurate are the representations? Some simulations of physical
events might prove to be 80 to 90 percent accurate, while other
phenomena, such as high-frequency wind noise, are extremely difficult to
model, Tilove said. The same is true of human factors software. When it
comes to size, reach, vision, and strength, digital manikins may be more
accurate than real human beings, according to Boeing's Rice. "There's
some amount of error inherent in every human model that approximates
human motion," he said. "We attempt to validate our models and report
the error, which might be 2 percent for certain types of reaches, 0.5
percent for others.

"But you can measure a person in the morning and their reach will
change by an inch or so by the afternoon. So there's probably more error
in individual measurements from one time of the day to another than
there is in our model."

Simulating the mechanical behavior of humans is fairly mature, Rice
said. After all, modeling the size of an arm and the rotation of its
elbow and wrist is not all that different than describing the movement
of a metal shank with two joints.

Simulating the Subjective

What is still missing, he said, are ways to simulate more subjective
factors, such as comfort and fatigue. "The field is moving toward
behavior issues," Rice explained. "Several systems have some of these
capabilities, such as a little red light that comes on and says the
manikin is more uncomfortable than it was before.

"But it's still very vague," he continued. "One person may be
perfectly comfortable in that situation while someone else is in pain.
There's very little objective data in this area. When someone decides
it's important enough to fund research to gather valid data, we'll start
seeing more capable software."

Jack, the male model from Engineering Animation, can be made to fit the profiles of
men with a range of percentile scores in size, strength, and other physical measures.

One way to overcome behavior barriers is to put real people in
simulations. Yet immersive virtual reality poses its own challenges,
starting with geometric complexity. "The amount of data we'd like to
manipulate is so big, even the fastest computers can't handle them,"
Tilove said. "That means you have to trade off image realism for speed
of response. In virtual interiors, we don't have enough resolution to
read the instrument gauges clearly. If we did, there would be way too
much data for the CAVE to respond to when you move your head around."

Tilove has a shopping list of other features he would like. Like many
members of large corporations, he'd like ways to run a single simulation
in several CAVEs around the world. The problem, he said, lies not so
much in visualization technology as in communica-tion etiquette.

"It's like a videoconference," he explained. "It works fine if you're
reviewing structured information that everyone's seen. But when you try
to collaborate, nobody knows what the other guys are looking at or who
talks next. We take a lot of cues from body language and all of that
goes away."

Better ways to manipulate virtual reality are also on Tilove's wish
list. He wants tactile as well as visual feedback, so viewers can
actually feel it when they bump into something. Some devices are
beginning to emerge which provide that capability, such as penlike
devices linked to pulleys and motors that simulate contact forces.

In the end, though, the field's most important issue is simply
putting human factors software into the hands of more engineers.

Today, the technology is limited to companies that do 3-D CAD
modeling. That may be changing with the advent of less expensive
visualization software. Visualization software does not create CAD
models, but it allows users to visualize CAD data.

Division Group produces a broad range of visualization software,
including dV/Manikin and dV/Safework digital humans, as well as
dV/Immersion for full-scale virtual reality modeling. Product marketing
director Ralph Mayer said he can provide visualization software for
$4,000 to $10,000 a seat.

It's not cheap. Yet it's significantly less costly than it was even
two or three years ago. Large companies, said Mayer, can now afford to
distribute visualization software throughout the organization. They can
even send models-minus their proprietary engineering data-to their
smaller suppliers.

This gives engineers who ordinarily don't have any input into design
a chance to test new products and processes for human factors very early
in their design. Ideally, it will lead to faster introduction of safer,
more comfortable, easier-to-use products.

It's a revolution in the making, one that suggests the frustrating
days for Jack and Jill are far from over.

This article is provided by Mechanical Engineering magazine, a publication of the
ASME.